Light-emitting surface element and method for producing a light-emitting surface element

ABSTRACT

A light-emitting surface element includes a connection device, a light-generating element having at least two electrical connections electrically conductively connected to assigned connection lines on the connection device, and at least one planar light-guiding element formed by injection-molding in a manner at least partly embedding an arrangement composed of connection device and light-generating element in the planar light-guiding element.

RELATED APPLICATIONS

This is a §371 of International Application No. PCT/DE2008/001589, withan international filing date of Sep. 26, 2008 (WO 2009/039846 A1,published Apr. 2, 2009), which is based on German Patent Application No.10 2007 046 520.5, filed Sep. 28, 2007, the subject matter of which isincorporated by reference.

TECHNICAL FIELD

This disclosure relates to a light-emitting surface element and to amethod for producing a light-emitting surface element.

BACKGROUND

Light-emitting surface elements have acquired great importance in therecent past. Light-emitting surface elements are desired not just incases where surfaces are to be illuminated areally as display elements,for example, but also in the case of a wide variety of types ofdisplays. Particular importance is attached to a uniform luminousdistribution of the light-emitting surface such that all regions areperceived equally. By way of example, LCD monitor and TFT displays,requiring areal transillumination, have existed for a relatively longtime. However, light sources are generally in point or line form, suchthat the light has to be distributed over the surface for arealillumination. For this purpose, planar optical waveguides are knownwhich, adapted to the distance from the light source by means of acorresponding surface treatment, couple the light out of the opticalwaveguide and cause it to be emitted.

For reasons of saving energy, in particular, it is endeavored to useconventional semiconductor components to generate light since they arehighly efficient. Semiconductor components of this type are also knownas LEDs.

It could therefore be helpful to provide a light-emitting surfaceelement, and a method for producing the latter, which can be producedwith high reliability in conjunction with low radiation losses.

SUMMARY

We provide a light-emitting surface element including a connectiondevice, a light-generating element having at least two connectionselectrically conductively connected to assigned connection lines on theconnection device, and at least one planar light-guiding element formedby injection-molding in a manner at least partly embedding anarrangement composed of connection device and light-generating elementin the planar light-guiding element.

We also provide a method for producing a light-emitting surface elementincluding providing a connection device, arranging a light-generatingelement on the connection device, and producing a planar light-guidingelement by injection-molding in such a way that the light-generatingelement and the connection device are at least partly embedded into thelight-guiding element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a light-emitting surface element in a partial side view.

FIG. 2 shows the light-emitting surface element illustrated in FIG. 1 asrotated by 90 degrees in a partial view.

FIG. 3 shows a plan view of the arrangement of light-emitting diodes ona strip-type connection device.

FIG. 4 shows a schematic illustration of a light-emitting surfaceelement with a plurality of light-emitting diodes.

FIG. 5 shows the strip material illustrated in FIG. 3 after having beenencapsulated by a planar light-guiding element by injection molding.

FIG. 6 shows a variant of the configuration illustrated in FIG. 1.

DETAILED DESCRIPTION

As a result of the production of the planar light-guiding element by theinjection-molding method, a light-generating element and a connectiondevice are embedded into the light-guiding element, such that, first,the coupling of light into the light-guiding element is made possiblewith high efficiency as a result of the avoidance of interfaces abuttingone another and, second, it is possible to form a stable connectionbetween the planar light-guiding element and the arrangement composed ofconnection device and light-generating element.

The provision of the light-generating element as “chip size package”makes it possible to mount the light-generating element easily and in amanner avoiding bonding wires that impede the mounting, and to haveavailable a free surface via which the light is coupled into the planarlight-guiding element.

The provision of a light-emitting diode as light-generating elementmakes it possible to generate light in the desired color by means of asuitable choice, such that different colored-luminous surfaces can beobtained with the same planar light-guiding element and only onecorresponding light-emitting diode has to be provided.

As a result of a conversion means being applied on the light-emittingdiode mounted as “chip size package” on the connection device, themounted arrangement is protected against impairments during injectionmolding. Furthermore, the coloration can thus be determined at a verylate time in production.

Our elements and methods are described below on the basis of exampleswith reference to the drawings. Identical reference symbols indicateidentical elements in the individual figures, but the illustrations donot show relationships to scale.

FIG. 1 shows an example wherein a flexible strip material 7 is provided,which has through openings 9 spaced apart at a constant distance.Conductor tracks 6 composed of electrically conductive material areapplied on the strip material 7. This application process can beeffected for example by printing technology or by lamination. In thiscase, the conductor track 6 can either firstly be applied over the wholearea and then acquire the desired form by means of an etching method,for example, or be applied directly in the desired form. Printingtechnology, in particular, is recommended for the latter option.

Furthermore, provision is made of a light-generating element such as anLED 3, for example, which is formed as a so-called “chip size package,”alternatively called CSP 1. In this case, CSP 1 consists of a carrier 2on which the LED 3 is formed. The connection contact-making of the LED 3is provided on the carrier 2 in a manner not illustrated in detail. Thecarrier 2 in turn has connection contacts connected to the conductortracks 6, for example, by means of flexible bumps 5. During operation,the LED 3 is then intended to emit visible electromagnetic radiationfrom the side remote from the carrier 2.

As an option, provision is made for applying a conversion layer 4 onthis surface which emits the light, the conversion layer altering thecoloration of the light. This means that the wavelength of the emittedlight is converted into a light having a different wavelength. In thisway, by way of example, blue light emitted by an LED can be convertedinto white light with high efficiency.

The arrangement described up to this point, composed of CSP 1 and stripmaterial 7 provided with conductor track 6, is then surrounded by aplanar light-guiding element 8, such that the arrangement is embedded inthe planar light-guiding element 8. This embedding is preferablyeffected in the form such that the preassembled arrangement composed ofCSP 1 and strip material 7 is introduced into an injection mold and theinjection mold is then filled by a thermoplastic material. Duringinjection molding, the thermoplastic material also penetrates throughthe through openings 9, thus resulting in an intimate and stableconnection between the planar light-guiding element 8 and the stripmaterial 7 after curing.

FIG. 2 shows this arrangement again in a manner rotated by 90 degrees.It can be discerned here that the planar light-guiding element 8 hasapproximately the thickness of the CSP 1. The extent to which the planarlight-guiding element 8 extends further on that side of the stripmaterial 7 which is remote from the CSP depends solely on mechanicalpreconditions.

Since the light is emitted from that side of the LED 3 which is remotefrom the carrier, the light does not propagate and is not passed onbelow the strip material 7. For reasons of stability or for reasons ofshaping, however, it may be desired to provide the injection-moldedmaterial not only as far as penetration through the strip material, butalso beyond that, as is indicated in the figures.

Two small elevations 10 are indicated at the surface of thelight-guiding planar element 8. The elevations are intended to indicatesurface configurations by means of which the light is coupled out.Normally, the light emitted by the LED is guided in the planarlight-guiding element 8 and reflected inward again as soon as the lightimpinges on the outer edge. If the light passes to locations which areidentified by the reference symbol 10 and modulate the surface, analtered angle of incidence is present for the light coming from insideat the surface such that the light is no longer reflected inward, butrather is emitted outward. In this way, the emission at the surface ofthe planar light-guiding element can be set by means of a correspondingconfiguration of the surface.

FIG. 3 shows the strip material 7 with the through openings 9 in planview. Conductor tracks 6 are led in pairs at uniform distances, theconductor tracks being led more closely to one another at the locationat which a CSP 1 is provided for mounting. Over and above their functiondescribed with reference to FIGS. 1 and 2, the through openings 9 arealso advantageous when the strip material 7 is populated in a mannercoming from a roll and is then intended to be rolled up again. Thethrough openings 9 can then be used for exact transport and/or for exactpositioning of the strip 7. This also holds true, of course, when thestrip material 7 is introduced into the injection mold and positionedthere. The window openings 11 serve to ensure that, during the injectionmolding, the planar light-guiding element can extend around the stripmaterial 7 and in this case, as can be discerned in FIG. 2, projectsonly insignificantly further beyond the CPS 1.

In FIG. 5, this more or less continuous arrangement from FIG. 3 isillustrated in a more highly simplified manner in a view correspondingto FIG. 1. The planar light-guiding element can be formed as it werecorrespondingly continuously like the strip and be divided at desireddistances for the purpose of separation after curing. In accordance withFIG. 5, a separating gap 10 is illustrated in each case centrallybetween two CSPs 1, along which gap the individual light-emitting planarelement is separated. This can be done by means of a suitable cuttingmethod, for example.

However, it is also conceivable either for a respective injection moldto be used for an individual light-emitting surface element or for theinjection mold to be configured in such a way that it has taperedportions or partitions, such that the individual light-emitting surfaceelements can correspondingly be separated by breaking-off, ifappropriate, at the locations provided with the reference symbols 10 inFIG. 5.

However, it is also not absolutely necessary that only an individuallight-generating CSP 1 is provided for each light-emitting surfaceelement. The number depends ultimately on the desired luminous intensityand the size of the surface to be formed and illuminated. In accordancewith FIG. 4, this is indicated in a form such that three CSPs 1 arechosen in the case of the example illustrated in FIG. 4.

Referring to FIG. 1, it is indicated that a conversion layer 4 isapplied on the LED 3 to convert the natural light generated by the LEDinto a desired light. In a configuration such as is illustrated in FIG.6, the arrangement differs from the arrangement illustrated in FIG. 1only insofar as initially the conversion layer 4 is absent. Instead ofthis, a conversion covering 4 a is applied in a manner enveloping theCSP 1. This can be applied, for example, as a drop or in an injectionmethod. Which method is ultimately chosen depends solely on thetechnical possibilities and on the state in which the CSP 1 is intendedto be tested beforehand prior to mounting on the strip material.

1-10. (canceled)
 11. A light-emitting surface element comprising: aconnection device; a light-generating element having at least twoconnections electrically conductively connected to assigned connectionlines on the connection device; and at least one planar light-guidingelement formed by injection-molding in a manner at least partlyembedding an arrangement composed of connection device andlight-generating element in the planar light-guiding element.
 12. Thelight-emitting element as claimed in claim 11, wherein thelight-generating element is a light-emitting diode formed as a chip sizepackage.
 13. The light-emitting surface element as claimed in claim 12,wherein the chip size package has a carrier with connection elements andlying opposite the latter on the carrier a light-emitting diode chipelectrically conductively connected to the connection elements.
 14. Thelight-emitting surface element as claimed in claim 11, wherein alight-emitting region of the light-generating element is covered by aconverter that converts the light emitted with a first wavelength by thelight-generating element into a light having a wavelength differenttherefrom.
 15. The light-emitting surface element as claimed in claim14, wherein the converter is formed as a layer covering thelight-emitting region on the chip.
 16. The light-emitting surfaceelement as claimed in claim 14, wherein the converter is formed in amanner covering the chip size package on the carrier.
 17. Thelight-emitting surface element as claimed in claim 11, wherein theconnection device is formed from a strip material and connection linesarranged on the strip material and has openings at regular distancesalong a longitudinal extent, through which openings the light-guidingsurface element projects integrally.
 18. The light-emitting surfaceelement as claimed in claim 11, wherein a plurality of light-generatingelements are provided on the connection device.
 19. The light-emittingsurface element as claimed in claim 12, wherein a light-emitting regionof the light-generating element is covered by a converter that convertsthe light emitted with a first wavelength by the light-generatingelement into a light having a wavelength different therefrom.
 20. Thelight-emitting surface element as claimed in claim 13, wherein alight-emitting region of the light-generating element is covered by aconverter that converts the light emitted with a first wavelength by thelight-generating element into a light having a wavelength differenttherefrom.
 21. The light-emitting surface element as claimed in claim12, wherein the connection device is formed from a strip material andconnection lines arranged on the strip material and has openings atregular distances along a longitudinal extent, through which openingsthe light-guiding surface element projects integrally.
 22. Thelight-emitting surface element as claimed in claim 13, wherein theconnection device is formed from a strip material and connection linesarranged on the strip material and has openings at regular distancesalong a longitudinal extent, through which openings the light-guidingsurface element projects integrally.
 23. The light-emitting surfaceelement as claimed in claim 14, wherein the connection device is formedfrom a strip material and connection lines arranged on the stripmaterial and has openings at regular distances along a longitudinalextent, through which openings the light-guiding surface elementprojects integrally.
 24. The light-emitting surface element as claimedin claim 15, wherein the connection device is formed from a stripmaterial and connection lines arranged on the strip material and hasopenings at regular distances along a longitudinal extent, through whichopenings the light-guiding surface element projects integrally.
 25. Thelight-emitting surface element as claimed in claim 16, wherein theconnection device is formed from a strip material and connection linesarranged on the strip material and has openings at regular distancesalong a longitudinal extent, through which openings the light-guidingsurface element projects integrally.
 26. A method for producing alight-emitting surface element comprising: providing a connectiondevice; arranging a light-generating element on the connection device;and producing a planar light-guiding element by injection-molding insuch a way that the light-generating element and the connection deviceare at least partly embedded into the light-guiding element.
 27. Themethod as claimed in claim 26, wherein the connection device is providedas a continuous material, and the individual light-emitting surfaceelement is separated after curing of the injection-molded planarlight-guiding elements.